Hermetically sealed electrical terminal

ABSTRACT

A hermetically sealed electrical terminal in which one or more highly conductive conductor pins, formed from materials such as copper and copper alloys, are electrically insulated from a supporting member, such as a metallic shell, by means of a molded dielectric sealing member which coacts with the conductor pins and the supporting member to provide a reliable hermetic seal.

ilite Dozier Nov. 6, 1973 [54] gggxgifi SEALED ELECTRICAL FOREIGNPATENTS OR APPLICATIONS 284,897 2/1928 Great Britain 174/142 [75]Inventor: Hilliard Dozier, Cincinnati, Ohio 499,872 11/1954 ltaly174/153 R [73] Assignee: U.S. Terminals, inc, Cincinnati, OTHERPUBLlCATlONS Ohio Wyzeenbeek, Hermetic FeedThrough Terminals, [22]Filed: 6, 1971 Electrical Manufacturing, Jan. 1954, pages 129-131.

[ PP 204,855 Primary Examiner-Laramie E. Askin Attorney-John W. Melvilleet al. [52] US. (31....174/153 R, 339/126 R, 339/192 RL,

[51] 1112. C1. H0lr 9/16, HOlb 17/26 A h m i lly le ele l rmin l inwhich one [58] Field of Search l74/50.61, 52 S, or more g y conductiveconductor p formed 174/142, 153 R; 339/126 R, 192 RL, 218 R, frommaterials such as copper and copper alloys, are 218 C 218 M electricallyinsulated from a supporting member, such as a metallic shell, by meansofa molded dielectric seal [56] Referen e Cited ing member which coactswith the conductor pins and UNITED STATES PATENTS the supporting memberto provide a reliable hermetic 2,748,187 5/1956 Conrad 174 153 R Seal3,522,575 8/1970 Watson at 211...... 339/126 R X 14 Claims, 6 DrawingFigures HERMETICALLY SEALED ELECTRICAL TERMINAL BACKGROUND OF THEINVENTION The present invention relates to electrical terminals of thetype wherein one or more conductor pins project through and are securedto a supporting body by means ofa seal which electrically insulates theconductor pins from the supporting body and at the same timehermetically seals the pins against the exchange of atmosphere betweenone side of the terminal body and the other. Such terminals are widelyused in refrigeration headers, for example, wherein an electricalconnection is made with components mounted within a sealed receptacle orchamber. Such terminals also find wide usage in transformers, relays,switches, circuit breakers, heaters, communications equipment, andspace'vehicle accessories.

The great bulk of hermetically sealed terminals in current use are ofwhat may be called a hard seal type, in which the conductor pins aremounted in the supporting body by means of a glass-to-metal orceramic-to-metal seal. Such terminals, while providing an effectivehermetic seal, are subject to a number of disadvantages. A principaldisadvantage lies in the limitations imposed upon the materials fromwhich the conductor pins may be formed. While copper and copper alloyconductor pins are ideal conductors of electricity, they cannot besuccessfully used with glass or ceramic seals due to differences in thecoefficients of expansion between the conductor pins and the sealingmaterial. In order to minimize the problem, conventional hermeticterminals of the hard seal type employ conductor pins formed fromstainless steel, stainless steel with a copper core, or nickel alloys.However, pins formed from these materials have an extremely lowpercentage of conductivity as compared with comparable size pins formedfrom copper or a copper alloy. As a result, terminals utilizing steelconductor pins must be substantially larger than would be required werethe conductor pins formed from copper or other materials having greaterconductivity.

Terminals incorporating glass or ceramic seals are also subject to beingcracked or broken if roughly handled or if the pins are bent duringinstallation. If the seals are cracked or broken, the hermetic barrierbetween the pins and their supporting structure is impaired ordestroyed, as is the ability of the seals to electrically insulate theconductor pins relative to the support in which the pins are mounted. Inaddition, it has not heretofore been possible to repair conventionalhard seal terminals where such repairs involve a heat generatingoperation, such as brazing or resistance welding, because of thecritical temperature considerations involving the expansion andcontraction of the parts.

Various expedients have been proposed to overcome the shortcomings. ofthe hard seal" terminals, but such expedients have met with only limitedsuccess. For example, US. Pat. No. 3,160,460, dated Dec. 8, I964, andentitled Terminal Assembly Having Conductor Pins In Terminal Block,teaches an essentially hard seal" terminal having a glass-to-metal sealcovered on the outer side of the terminal by a resilient insulatorbonded to th support and adjacent portions of the conductor pins. Sucharrangement does not, however, overcome. the expansion problem betweenthe conduc tor pins and their glass seals. In addition, theconfiguration of the seals is still limited to the flow and wettingcharacteristics of the glass, which in turn limits the ability of theseals to meet long path arc resistance requirements in spite of themolded overlay.

Efforts have also been made to mold the seals from various distortabledielectric materials to provide what may be called a soft seal terminal,but such terminals have been unsuccessful due primarily to theirinability to withstand high pressure, as well as other environmentalconditions, such as elevated temperatures. These failures are believeddue in large measure to plastic flow and creep of the distortablematerials from which the seals are formed. One solution to the problemsencountered in soft seal terminals is taught in US. Pat. No. 3,605,076,dated Sept. 14, 1971, and entitled Hermetically Sealed TerminalConstruction, which teaches a terminal construction of the soft sealtype in which each conductor pin is electrically insulated andhermetically sealed relative to its support by means of a distortabledielectric sealing member incapsulated between a pair of essentiallyrigid dielectric caps. While such arrangement provides a highlyeffective hermetic seal, the cost of producing the terminals isrelatively high due to the number of parts involved and the laborrequired to assemble them.

In contrast to the foregoing, the present invention provides a terminalconstruction of essentially the soft seal type in which each conductorpin is effectively sealed to its surrounding support by a unitary moldeddielectric sealing member which is free from the disadvantagesheretofore encountered in molded soft seal terminal constructions, theconfiguration of the con ductor pins together with the configuration ofthe sealing members and their relationship to the supporting body of theterminal coacting to provide a highly effective hermetic seal which canbe efficiently and inexpensively manufactured and the seal configured toprovide the desired arc resistance.

RESUME OF THE INVENTION The present invention contemplates a terminalconstruction wherein a unitary sealing member is integrally molded toeach conductor pin and its surrounding support, the construction andarrangement of parts being such that expansion and contraction of themetallic parts does not interfere with or otherwise adversely affect thebond between the sealing member and the metallic parts.

To implement the foregoing, the conductor pins are provided with aplurality of shoulders which materially increase the bonding surfaceareas of the pins and which are positioned to effectively control thelocation and degree of contraction of the sealing material as it ismolded and cured, as well as control plastic flow and creep aftermolding.

In similar fashion, the molded sealing member is of a configuration suchthat it effectively insulates both the conductor pin and the supportingbody in all critical areas, the parts being configured to take advantageof the natural contraction of the sealing material during molding toinsure a positive and tight seal between the metallic parts and thesealing material.

While the terminals of the present invention may be characterized asbeing ofthe soft seal type in that they are not frangible in the senseof a glass or ceramic seal, the sealing members may be formed frommaterials which are essentially hard and rigid when cured. For example,epoxy molding compounds provide excellent seals, yet they are not softin the sense of being readily distortable. They are, however,sufficiently compliant to accommodate expansion and contraction of theconductor pins. On the other hand, the sealing members may be formedfrom materials which are relatively soft and readily distortable, suchas synthetic elastomers. A key consideration in the formation of theseal is the use of a sealing material which, in addition to providingthe required dielectric properties, is capable of maintaining a tightbond with both the conductor pins and the supporting body irrespectiveof environmental conditions, such as elevated temperatures. This permitsthe use of copper and copper alloy conductor pins, which result in asubstantial reduction in the size of the conductor pins for a givencurrent conducting capacity. The invention thus facilitatesminiaturization in that comparable, or even greater, conductivecapacities can be achieved utilizing conductor pins of much smallersizes formed from any conductive material hav ing a higher conductivecapacity than the conductor pins currently in use.

The present invention may be utilized in conjunction with singleormultiple pin terminals, or in constructions wherein the body or supportfor the conductor pins comprises an integral part of a housing or othersealed component to which electric current is to be supplied.

DESCRIPTION OF THE DRAWINGS FIG. l is a top plan view of an exemplaryterminal construction in accordance with the invention, the illustratedterminal comprising a three-conductor header of the type used incompressors for refrigeration equipment.

FIG. 2 is a vertical sectional view taken along the line 2--2 of FIG. 1.

FIG. 3 is a bottom plan view of the terminal construction illustrated inFIGS. l and 2.

FIG. 4 is a vertical sectional view of a modified conductor pin in whichthe shoulders which engage the sealing material are undercut.

FIG. 5 is an elevational view of another form of conductor pin. I

FIG. 6 is a vertical sectional view similar to FIG. 2 but illustrating aconstruction wherein the supporting body for the terminal is an integralpart of a housing or like receptacle.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring first to FIG. 2 of thedrawings, the terminal comprises a supporting member or body 1 which, inthe embodiment illustrated, is of cup-shaped configuration, having anannular body wall 2 terminating at one end in an outturned mountingflange 3 and at its opposite end in a base 4 interrupted by spaced apartsleeves or sockets 5 lying within the confines of the annular body wall2. The configuration of the body member 1 is conventional for athree-pin header and can be formed of any material suitable for thepurpose, although for most installations a steel body is preferred sinceit is relatively inexpensive and can be easily formed into the desiredshape. The particular material from which the body member is formed willbe governed in large measure by the mode of installation of theterminal, de-

pending upon whether it is to be welded, soldered, brazed, threaded,press-fitted, or even adhesively secured in place.

The supporting member 1 mounts a plurality of conductor pins 6 whichextend axially through the sleeves 5, the conductor pins being securedin place and hermetically sealed by means of the sealing member 7, whichis a unitary member composed of a dielectric material molded in situ tothe desired configuration.

The conductor pins 6 may be formed from substantially any electricallyconductive material, although copper or copper alloy pins are preferredbecause of their high electrical conductivity. Since expansion andcontraction of the pins does not pose a problem due to the manner inwhich the pins are mounted and the nature of the sealing material, awide choice of conductor pin materials is available, depending upon thedesired strength, size and conductive capacity of the pins.

The sealing member 7 is formed from a dielectric material capable ofbeing molded in situ to the supporting body 1 and conductor pins. Keyconsiderations in the selection of the molding compound are theprovision of a material having sufficiently low resistance to flow sothat its direction and extent of flow may be controlled during molding,and having a coefficient of linear expansion which is compatible withthe coefficient of expansion of the conductor pins. Essentially, thedirection of flow of the molding material is controlled by the design ofthe terminal, which takes full advantage of the normal shrinkage orcontraction of the molding material during the molding operation. Epoxymolding compounds have been found to produce excellent results,particularly when fortified with mineral or glass fibers. By way ofexample, excellent results have been achieved using epoxy moldingcompounds manufactured by Allied Chemical Corporation under thetrademark EPIALL. While the epoxy molding compounds are essentiallyrigid when cured, they are nonetheless compatible with conductor pinsformed from copper or copper alloys insofar as their coefficients ofexpansion are concerned and an excellent hermetic seal results. However,distortable dielectric material, i.e., materials which are relativelysoft and capable of being readily flexed, also may be employed, such assynthetic rubber. An example of a synthetic elastomer suitable for thepurpose is chlorosulfonated polyethylene manufactured by E. I. DuPont deNemours & Co. under the trademark I-IYPALON. It should be noted thatwhere a material such as HYPALON is used, a bonding adhesive is requiredto insure a tight bond between the metal parts and the seal.

In order to take full advantage of the flow and shrinkagecharacteristics of the molding compound and insure a positive seal withthe metallic components of the terminal, the following designconsiderations are important if a hermetic seal is to be achieved:

1. The sealing member 7 includes annular portions 8 which surround thesleeves 5 of the supporting body, so that contraction of the outerportions 8 of the sealing member during curing will cause the sealingmaterial to tightly bond to the outside surfaces of the sleeves. Inaddition, the annular portions 8 of the sealing member are relativelythin in cross-section and hence will readily expand and contract withthe metallic sleeves without separation of the tight bond which has beenformed. If the annular portions 8 were massive, i.e., relatively thickin cross-section, the added mass would tend to hold the portions 8against compliant expansion and contraction.

2. The conductor pins 6 are provided with a plurality of shoulders 9,I0, and 11 which increase the bonding surface area of each conductor pinand assist in con.- trolling the location and degree of contraction ofthe sealing member, particularly the intermediate porton 12 thereoflying withn the confines of the sleeve 5. Thus, the shoulders 9 and 10,which may be conveniently defined by annular flanges machined in theconductor pin, effectively lie at opposite ends of the sleeve 5 and actto anchor the sealing material within the confines of the sleeve, i.e.,resist flow or creep of the sealing material axially of the sleeve,thereby rendering the intermediate portion 12 of the sealing memberlying within the confines of the sleeve relatively unaffected byexpansion and contraction of the conductor pin and the surroundingsleeve.

3. The shoulders 9 and 10, as well as the shoulder 11, serve to resistcontraction of the larger masses of sealing material lying outwardlybeyond the ends of the intermediate portion 12 in directions which wouldtend to elongate and hence contract the intermediate portion 12. Theshoulders also serve as anchors to enhance the pull resistance i.e.,axial displacement of the conductor pin.

4. The conductor pins are also preferably provided with a tapered orbeveled section 13 positioned to encourage contraction of the relativelylarge external mass of sealing material toward the base 4 of the bodymember so as to effect and maintain a tight bond therewith.

5. Each conductor pin is also provided with a knurl 14, preferablypositioned between the shoulders 9 and 10, the knurl 14 serving the dualfunction of preventing rotation of the conductor pin and at the sametime in creasing the surface area of the pin to which the sealing memberbonds. Being positioned within the confines of the sleeve 5, the knurledportion 14 is effectively within the tranquil" intermediate portion 12of the sealing member whereby expansion and contraction of the sealingmember is under maximum restraint.

6. On its undersurface and as best seen in FIG. 3, the sealing member isprovided with an enlarged center portion 115 and mold ring portions 16interconnecting the sleeve-surrounding outer portions 8, the portions115 and 16 providing non-critical areas of the seal to whichimperfections caused by entrapped gases or other contaminants mayreadily migrate. The portions 15 and 16 also assist in increasing thebonding surface between the sealing member and the supporting body ll,particularly on the undersurface of base 4 and hence effectivelyincrease the strength of the bond in the critical areas of the seal.

7. It has also been found desirable to provide the sealing member withintegral collars l7 and 18 surrounding the conductor pins at the pointwhere the opposite ends of the pins emerge from the sealing member, suchcollars acting to relieve stress concentrations which could result inaging cracks in the peripheral areas immediately surrounding theconductor pins. The collars also serve as steps against which a plug orthe like for receiving the conductor pins may be seated.

With the foregoing design considerations in mind, it will be evidentthat the size and dimension of the parts may be varied as required for agiven application, inclusive of the spacing of the parts to provide theoversurface distance required to meet Underwriter Laboratoryrequirements or other similar specifications. As will also be evident,the instant design is equally applicable to single or multiple pinterminals, which may be supplied in various body configurations andvarious pin configurations. For example, the pins may be provided withconductor tabs 19 at one or both ends, as required for any giveninstallation.

FIG. 4 of the drawings illustrates a modified conductor pin constructionwherein each of the shoulders 9, 10, and 11 undercut, as indicated at20, the undercut surfaces acting to take further advantage of thecontraction of the sealing member during curing. This is especiallydesirable where elastomeric seals are employed which are more readilydistortable than the essentially rigid epoxy compounds. The undercutsalso act as anchors to resist severe pull pressures axially of the pin.

FIG. 5 illustrates still another conductor pin construction in which thepin configuration has been greatly simplified, the pin having distalends 21 and 22 separated by an intermediate portion 23 of lesserdiameter, the innermost ends of the distal portions 21 and 22 definingshoulders 9a and 10a which will function in the manner of the shoulders9 and 10 previously described. In order to increase the effective bondbetween the intermediate portion 23 and the surrounding sealing member,the portion 23 may be sandblasted to provide a roughened surface 24.Alternatively, the intermediate portion of the pin may be provided witha knurled portion similar to the knurled portion 14 illustrated in FIG.2.

FIG. 6 illustrates an application of the invention wherein the supportor body la of the terminal comprises an integral part of a housing orother receptacle containing an electrical component to be electricallyconnected to a source of current outside the confines of the receptacle.In this instance, the terminal illustrated has a single conductor pin 6extending through the sleeve 5a formed as an integral part of thehousing or receptacle lla. It will be evident, however, that the sealingmember 7a effectively surrounds the sleeve 5a, with the shoulders on theconductor pin acting to control the location and extent of contractionof the sealing member during molding. Obviously, any desired number ofconductor pins may be mounted in the receptacle Ia, either independentlyor with their sealing members joined together as an integral seal.

It should be readily apparent that various additional changes andmodifications may be made in the structural details of the terminals,within the scope of the appended claims, without departing from thespirit and purpose of the invention.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:

l. A hermetically sealed terminal comprising a support member having abase with at least one annular opening therein defining one end of agenerally cylindrical sleeve projecting outwardly from one side of saidbase, an elongated conductor pin extending centrally through said sleeveand lying in spaced relation thereto, and a one-piece molded dielectricsealing member securing said conductor pin to said supporting member,said sealing member having an intermediate portion extending throughsaid sleeve in sealing engagement with said conductor pin and the innersurface of said sleeve,

said conductor pin having a pair of spaced apart opposingshoulder-forming faces positioned near the opposite ends of said sleeveto restrain the intermediate portion of said sealing member againstexpansion and contraction, said sealing member having integral outerportions extending outwardly beyond said intermediate portion on bothsides of said base, said outer portions being of larger diameter thansaid intermediate portion and surrounding said pin in sealing engagementtherewith, one of said outer portions having a relatively thin annularwall portion completely surrounding said sleeve in sealing engagementwith the outer surface thereof and in sealing engagement with said basein the area immediately surrounding said sleeve so as to incapsulatesaid sleeve therein, the other of said outer portions being in sealingengagement with the opposite side of said base in the area surroundingsaid annular opening.

2. The terminal construction claimed in claim 1 wherein said conductorpin has a central portion of reduced diameter as compared with itsopposite end portions, said pair of spaced apart shoulder-forming facesbeing defined at the junctures of the outer portions of the pin withsaid reduced diameter central portion, said faces being of no greaterdiameter than the opposite end portions of said conductor pin.

3. The terminal construction claimed in claim 2 wherein the centralportion of said conductor pin is roughened to enhance the engagement ofsaid sealing member with the central portion of said pin.

4. The terminal construction claimed in claim 1 wherein said conductorpin has an inwardly tapered portion lying outwardly beyond theshoulder-forming face in closest proximity to the base of saidsupporting member.

5. The terminal construction claimed in claim 4 wherein said conductorpin includes a third shoulderforming face lying within the confines ofthe outer portion of the sealing member which surrounds said sleeve.

6. The terminal construction claimed in claim 5 wherein the outerportions of said sealing member terminate at their outermost ends inintegral collars surrounding said pin.

7. The terminal construction claimed in claim 1 wherein said supportingmember has a plurality of sleeves projecting outwardly from one side ofsaid base, wherein a conductor pin extends centrally through each ofsaid sleeves, and wherein said one-piece sealing member has intermediateand outer portions associated with each of said sleeves.

8. The terminal construction claimed in claim 7 wherein the outerportions of said sealing member which completely surround said sleevesin sealing engagement with the outer surfaces thereof are interconnectedby a mold ring portion in sealing engagement with said base.

9. The terminal construction claimed in claim 8 wherein said relativelythin annular wall portions of said sealing member are alsointerconnected by an integral portion in sealing engagement with saidbase and spaced inwardly from said mold ring portion.

10. The terminal construction claimed in claim 7 wherein the base ofsaid supporting member terminates outwardly in an annular wallsurrounding said sleeves, and wherein the relatively thin annular wallportions of said sealing member which surround the outer surfaces ofsaid sleeves are free from contact with the annular wall of said base.

11. The terminal construction claimed in claim 1 wherein said sealingmember is essentially rigid.

12. The terminal construction claimed in claim 11 wherein said sealingmember is composed of an epoxy molding compound.

13. The terminal construction claimed in claim 1 wherein said sealingmember has a coefficient of expansion compatible with the coefficient ofexpansion of said terminal pin.

14. The terminal construction claimed in claim 13 wherein said terminalpin is formed from copper.

1. A hermetically sealed terminal comprising a support member having abase with at least one annular opening therein defining one end of agenerally cylindrical sleeve projecting outwardly from one side of saidbase, an elongated conductor pin extending centrally through said sleeveand lying in spaced relation thereto, and a one-piece molded dielectricsealing member securing said conductor pin to said supporting member,said sealing member having an intermediate portion extending throughsaid sleeve in sealing engagement with said conductor pin and the innersurface of said sleeve, said conductor pin having a pair of spaced apartopposing shoulder-forming faces positioned near the opposite ends ofsaid sleeve to restrain the intermediate portion of said sealing memberagainst expansion and contraction, said sealing member having integralouter portions extending outwardly beyond said intermediate portion onboth sides of said base, said outer portions being of larger diameterthan said intermediate portion and surrounding said pin in sealingengagement therewith, one of said outer portions having a relativelythin annular wall portion completely surrounding said sleeve in sealingengagement with the outer surface thereof and in sealing engagement withsaid base in the area immediately surrounding said sleeve so as toincapsulate said sleeve therein, the other of said outer portions beingin sealing engagement with the opposite side of said base in the areasurrounding said annular opening.
 2. The terminal construction claimedin claim 1 wherein said conductor pin has a central portion of reduceddiameter as compared with its opposite end portions, said pair of spacedapart shoulder-forming faces being defined at the junctures of the outerportions of the pin with said reduced diameter central portion, saidfaces being of no greater diameter than the opposite end portions ofsaid conductor pin.
 3. The terminal construction claimed in claim 2wherein the central portion of said conductor pin is roughened toenhance the engagement of said sealing member with the central portionof said pin.
 4. The terminal construction claimed in claim 1 whereinsaid conductor pin has an inwardly tapered portion lying outwardlybeyond the shoulder-forming face in closest proximity to the base ofsaid supporting member.
 5. The terminal construction claimed in claim 4wherein said conductor pin includes a third shoulder-forming face lyingwithin the confines of the outer portion of the sealing member whichsurrounds said sleeve.
 6. The terminal construction claimed in claim 5wherein the outer portions of said sealing member terminate at theiroutermost ends in integral collars surrounding said pin.
 7. The terminalconstruction claimed in claim 1 wherein said supporting member has aplurality of sleeves projecting outwardly from one side of said base,wherein a conductor pin extends centrally through each of said sleeves,and wherein said one-Piece sealing member has intermediate and outerportions associated with each of said sleeves.
 8. The terminalconstruction claimed in claim 7 wherein the outer portions of saidsealing member which completely surround said sleeves in sealingengagement with the outer surfaces thereof are interconnected by a moldring portion in sealing engagement with said base.
 9. The terminalconstruction claimed in claim 8 wherein said relatively thin annularwall portions of said sealing member are also interconnected by anintegral portion in sealing engagement with said base and spacedinwardly from said mold ring portion.
 10. The terminal constructionclaimed in claim 7 wherein the base of said supporting member terminatesoutwardly in an annular wall surrounding said sleeves, and wherein therelatively thin annular wall portions of said sealing member whichsurround the outer surfaces of said sleeves are free from contact withthe annular wall of said base.
 11. The terminal construction claimed inclaim 1 wherein said sealing member is essentially rigid.
 12. Theterminal construction claimed in claim 11 wherein said sealing member iscomposed of an epoxy molding compound.
 13. The terminal constructionclaimed in claim 1 wherein said sealing member has a coefficient ofexpansion compatible with the coefficient of expansion of said terminalpin.
 14. The terminal construction claimed in claim 13 wherein saidterminal pin is formed from copper.